1. Field of the Invention
This invention relates to a procedure for building a pseudo LAN (Local Area Network) system by using a plurality of point-to-point communication links in a distributed data process environment. The procedure particularly makes dynamic node configuration possible.
2. Prior Art
Along with recent diffusion of work stations, communication and distribution process among work stations based on a LAN system have widely been used, and various applications based on an interface specified for the standard LAN system are being rearranged. In concert with this, the need for geographical distribution and extension of the location for using a work station has been increased, and various procedures for combining a LAN system with point-to-point communication lines of a wide area network and various procedures for offering a LAN interface on a point-to-point line to form a pseudo LAN system have been developed to remove restrictions on the distance and constituent nodes of the LAN system.
In a point-to-point line, process of a layer-3 (network layer), which does not essentially exists in a LAN system, is necessary. Most existing procedures assume a static network and do not refer to the problem on process of the layer-3 (for example, JA PUPA 63-146536). Some existing procedures attempt to solve the problem by giving a significance to control of the layer-3 in a certain form and by incorporating it into an existing interface (for example, ISDNBIOS employed by the IBM ISDN adaptor employs a procedure for setting and releasing physical links at the same time as setting and releasing data session. ISDNBIOS is described in User's Guide: ISDN Co-Processor Support Program, and ISDNBIOS Interface Description: ISDN Co-Processor Support Program, published by International Business Machines Corporation in U.S. A.) The former, which does not consider that each node may be highly autonomous, is not economical particularly in such an environment that each user has one work station and does not often performs communication. The latter, which adds those beyond the intrinsic process of a LAN system to the LAN interface, imposes restrictions on the use of wide existing LAN applications on a point-to-point line (for example, ISDNBIOS referred to above imposes such a limitation that only one logical data link is permitted to extend to each physical link.)
At present, some systems make remote access to a LAN system possible, such as connection technique among a plurality of remote LAN systems by split bridges based on the LAN bridge defined by IEEE 802.1 and 802.5 committees, and LAN/ISDN interconnection technique being developed by IEEE 802.9 committee. The former, which assumes existence of a LAN system in each site, is not applicable in an environment with no LAN system. With the latter, which is intended principally to hide co-existence of systems by disclosing the LAN network interface to the part of the LAN system and the ISDN network interface to the part of the ISDN system, the use of LAN applications intended by pseudo LAN systems is impossible.